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Blood Test to Help Determine When Antibiotics Are Needed


blood testPeople often go to the doctor when they are suffering miserably from a respiratory illness to request antibiotics. Even though most respiratory infections (like the common cold or a flu) are a virus and antibiotics are ineffective on a virus, doctors prescribe them as a precaution, rather than tell the patient to take something over the counter, because they are uncertain whether the prescription may be warranted. However, researchers are working on a blood test to help determine when antibiotics are needed or not.

One cause largely cited for the growth of antibiotic-resistant bugs these days is overuse of antibiotics. Public health experts are urging doctors to prescribe them less, particularly in situations where they are unlikely to make a difference beyond placating the patient.

The fact is that doctors proffer antibiotics for approximately 75 percent of patients they see with runny noses, sneezes and coughs from respiratory ailments. This is even though infections like the flu and cold are viruses. However, there may also be a bacterial infection going on, such as a in the sinus or ear.

The new blood test that will be quick and “affordable” is being developed at Duke University School of Medicine in Durham, NC. The test eventually could be done in a doctor’s office to determine if the patient’s illness is caused by bacteria or by a virus. While not ready yet, the researchers are confident they are on the right track.

The research team tried the blood test out on 273 people with respiratory infections and 44 healthy people, as detailed by the team in the Jan. 20 issue of Science Translational Medicine. The test is designed to detect how genes “turn off and on in a particular pattern” when responding to a virus, bacteria, or some other cause. So, instead of analyzing the bacteria or viral cells themselves, it analyses the body’s reaction, which differs based on whether it is virat or something else.

The researchers believe that it will be a few years before the test is in use outside of testing. Getting results currently takes up to 10 hours, but they are confident that the time can be shortened to under an hour.

The test’s accuracy rate at distinguishing between infections that are bacterial or viral in nature was 87 percent. It is unique in its speed at presenting results while someone waits, and the accuracy is promising.

There are other tests that were developed, but they have proven to be problematic. There is an existing test that analyzes inflammation, but is not widely used and only has a 78 percent accuracy rate. Another test requires growing a culture of microbes for one to three days, which is too long for most people who are sick to wait. Still another test looks for the presence of certain bugs, but someone may test positive for something that is not be the main source of their suffering.

Cutting back on unnecessary use of the antibiotics is a priority for health professionals, including the World Health Organization. A clear diagnosis using the blood test could help practitioners better determine when antibiotics are needed and stop offering them as a catch-all therapy.

Written and edited by Dyanne Weiss

Science Translational Medicine; Host gene expression classifiers diagnose acute respiratory illness etiology
Forbes: Under The Weather? A Drop Of Blood Can Tell If Antibiotics Are Needed
TIME: A Blood Test May Soon Tell If You Really Need Antibiotics
U.S. News & World Report: Blood Test Might Predict When Antibiotics Won’t Help

Photo courtesy of Tom Mallinson – Creative Commons license